Stand at the top of the Rock of Gibraltar, 426 metres above the sea, and you are standing on the site of one of the most expensive jokes in the territory's history. A governor built a tower here to watch the Spanish fleet at Cadiz. Cadiz could not be seen. Lightning then finished what geography had started, and a century later a gun crew knocked the ruin down to settle an argument. That is the story the guides tell, and most of it holds up. Some of it does not. The tower was real, the failure was real, and the demolition in 1888 is a matter of record. But the ship usually named as the culprit had already sunk, twice over, and the dates people quote for the tower do not sit comfortably beside the dates of the man it is named after. Here is what actually happened, what is disputed, and how to stand on the spot yourself. Charles O'Hara was born in Lisbon around 1740, the illegitimate son of an Irish peer, and he had one of the strangest careers in the British Army. At Yorktown in 1781 he carried out the surrender on behalf of Lord Cornwallis, who pleaded illness, which means O'Hara personally handed over a British army in front of George Washington. Twelve years later, at the siege of Toulon, he was wounded and taken prisoner by French troops commanded by a young artillery officer named Napoleon Bonaparte. He spent nearly two years locked in the Luxembourg in Paris through the Terror, and was exchanged in 1795. Within months he was Governor of Gibraltar, a post he held from 30 December 1795 until his death in February 1802. The garrison called him the Old Cock of the Rock. He was theatrical, generous, famously hospitable, and by most accounts a genuinely effective governor at a dangerous moment for the fortress. He is also one of only two governors actually buried in Gibraltar, and his memorial is still in the King's Chapel. > A man who had surrendered a British army to Washington and then his own sword to Bonaparte was never going to be modest about what he built at the summit. O'Hara's idea was simple and, on paper, excellent. Gibraltar's problem in any war with Spain was intelligence. The Spanish fleet lay at Cadiz, and the first the garrison usually knew of a sortie was when sails appeared in the Strait. Put an observation tower on the very top of the Rock, O'Hara reasoned, and lookouts could watch the harbour at Cadiz directly and hand the garrison days of warning. The tower was built of hewn stone and iron, and it was originally given the respectable name of St George's Tower. Cadiz sits about 60 miles away, roughly 97 kilometres, in a straight line up the Atlantic coast. That distance is the whole problem, and O'Hara appears to have been the only man on the Rock who did not see it coming. Two things defeat the plan, and either one on its own is fatal. The first is the ground in between. The coast running north from Tarifa towards Cadiz is not flat. Hills and sierras rise between the Rock and the bay, and the harbour at Cadiz sits low and behind them. No amount of height at the Gibraltar end lifts a sightline over high ground standing in the way that far off. The second is the curve of the earth. From 426 metres the geometric horizon in ordinary conditions falls somewhere around 74 kilometres. Cadiz at roughly 97 kilometres is well beyond it. Even across a perfectly flat sea with nothing at all in the way, the harbour would have been below the horizon and out of sight. Add the Rock's own weather and it gets worse again. On easterly days the summit vanishes into the levanter cloud that forms over the ridge, which we explain in our guide to [the Gibraltar levanter cloud](/blog/gibraltar-levanter-cloud-explained). A lookout post on the top of the Rock spends a good many days of the year inside a cloud, watching nothing. Not long after it was finished, a violent storm drove a lightning bolt into the tower and wrecked it. Accounts hold that a sentinel on duty was killed. That detail is repeated almost everywhere and sourced almost nowhere, so treat it as garrison tradition rather than record, but the strike itself and the damage are reported consistently. The garrison, who had watched the money go up the hill and the view fail to arrive, renamed the place with the economy soldiers reserve for their commanding officers. St George's Tower became O'Hara's Folly. The ruin stayed up there, unrepaired, for most of the nineteenth century, a landmark that meant the opposite of what its builder intended. This is the part the guidebooks skip. Two details in the standard version do not survive a check. The first is the date of construction. The most repeated version has the tower going up between 1787 and 1791, ordered by O'Hara as Lieutenant Governor. But O'Hara was not appointed Lieutenant Governor of Gibraltar until 1792, and did not become Governor until the end of 1795. Either those construction dates are wrong, or the tower predates his command and he only completed or enlarged it. The sources contradict one anoth